Home office business-use calculator
Work from home? Some of your household bills are partly business costs. Enter your monthly bills and how you split them. You get the business part for each bill, a yearly total, and a comparison with the flat-rate option in the US or the UK. Nothing you enter is sent anywhere. It is saved only in this browser.
This is an estimate, not tax advice. What you can claim depends on your country, your business and how the space is used. Check the official pages below or ask a tax professional before you file.
Result
| Bill | Share | Business / month | Business / year |
|---|
Amounts are rounded to the nearest cent or penny. The yearly figure is the monthly figure × 12.
Compare with the flat rate
IRS simplified option: $5 per square foot of the area used for business, up to 300 square feet (maximum $1,500). The space must be used regularly and exclusively for business. Employees cannot claim it.
Enter the area used for work.
HMRC simplified expenses for the self-employed working 25 hours or more a month at home: £10 (25–50 hours), £18 (51–100 hours), £26 (101+ hours) per month. The flat rate does not include phone or internet, so those are added from your own split.
Enter your hours.
How to choose a fair split
- Rent, mortgage interest, insurance: the floor area used for work ÷ the whole home.
- Electricity and heating: the area share, or the area share adjusted for how much of the time the room is used for work.
- Phone and internet: a sample month of calls or hours online for work.
- Write down how you got each number and keep it with your bills. A percentage with a reason is much easier to explain later.
Step-by-step spreadsheet version (Excel and Google Sheets): How to work out the business-use share of home costs in a spreadsheet.
Sources (checked 21 October 2026)
General information only. This tool was built with the help of AI and checked with automated tests.
More free guides: MisaNeco Works blog (English) · Small business automation check